Hello, I am going to start doing my starters in a Erlenmeyer Flask and have begun shopping for them, I don't want to have to buy many different sizes so i was wondering could i get a big one, like 5000ml and do all of my starters in that? my recipes have ranged from needing a 1000ml starter to a 5000ml starter, i like the extra room for doing step up starters.

would there be a problem if i were to do a 1000ml starter in a 5000ml flask?

I have a 1000 and a 2000 ml flask. I have been using my 2000 on an electric burner. Big mistake: 1) Boil overs are an issue (even with fermcap-s). 2) my flask cracked and in my and other opinions was due to electric heat an crash cooling. So, use this info as you will. My future starters will be boiled in a standard sauce pan, chilled in an ice bath and transfered to a quart jar to be placed on the stir plate.

river water brewing wrote:would there be a problem if i were to do a 1000ml starter in a 5000ml flask?

No. Ideally, you probably want about 50% of the volume of the starter flask to be airspace to promote oxygenation anyway, so It will be fine. I guess the one concern, other than that a 5 L flask will be too small for a 5 L starter, is that the starters might be more oxidized with more head space. For that reason, I'd lean toward decanting the liquid from my starter before pitching .

The lore in the lab has always been that Pyrex® by Corning were the best, but I don't know that I've seen evidence to support that, and I've certainly broken Pyrex ones.

I think the secret is even heat and gradual cooling. I use a heated stir-plate that's designed for this, but if I was using an electric stove I'd use a heat diffuser. I've heard of people heating their flask on a cast-iron pan, which might accomplish the same thing. After that I never plunge the hot flask directly into ice water. I also allow it to cool for a while in the air before putting it into cold water to finish cooling.

I would either buy a heated dtirplate or stay away from direct heating of your flasks.
boiling in a nice shiny stainless boiler and transferring to a flask is probably the simplist and safest practice that will accomplish everything you need without risking your flask(s) JMO.

I had a flask (6l) break directly due to the concentrated heating of the element of an electric stove. I've since replaced the flask and the stove. The stove is still electric but now it's a glass top. No problems since. I've never had a problem with putting the hot flask into an ice bath. Of course this is lab glass and it's intended for this type of use.

Now here's a question; If you're using DME and RO water, possibly with nutrients, is there a real reason to boil? I've recently stopped the boiling practice and have had equally good results without the issues of boiling.